APPLICATION: Sheet properties are sensitive to the precise level of fiber character and sheet fines content. By manipulating the fiber and fines fractions, papermakers can improve sheet properties.

The surface structure and printability of radiata pine TMP sheets are sensitive to the character and content of their fractions of long fiber and fines. Sheets made from the fibers of juvenile wood are less porous and have smoother surfaces than sheets made from the fibers of mature wood. Therefore, the thin-walled fibers of juvenile wood generally produce sheets with better optical and printing properties.

In these experiments, the researchers tested the interrelated impacts that fiber size, fiber quality, and the quality, quantity, and type of fines have on the structure and print performance of sheets equivalent to newsprint. Most of their experiments were carried out on laboratory sheets formed from different pulps with freenesses of 100 mL CSF pulps. They determined the effects of the fines fraction by examining the relative influence of the primary and the secondary fines and by adding different quantities of fines to produce the required freeness.

They found that ink demand is more sensitive to fiber size and quality than to the pulp fines content, with the ink demand being lower for sheets characterized by juvenile wood. Increased quantities of fines increase the sheet density and decrease sheet porosity and roughness, reducing ink demand and improving print performance. By manipulating the quality and quantity of the fiber and fines fractions, papermakers can improve the performance of paper in printing. View this paper online at http://www.tappi.org/index.asp?pid=29478